You could consider moving the aggregator rule above the referring domains rule to give it priority over the referring domains rule - this way there would be no need for the exclusion on the referring domains rule.
It's probably better practice to do it this way round and may make it more simple to trouble shoot the issue e.g. if it you are not getting aggregator traffic you know it is because either the query string parameter is missing or does not contain the value you are looking for.
A couple of general points to note about using query string parameters in Adobe:
Query string parameters derived directly from the URL are not available on link tracking calls (i.e. only available on page views)
Sometimes adobe truncates variables so things can get lost if they are part of a very long URL/query string parameter. I think things get cut off at 255 characters during Adobe's processing of the data but I haven't tested this is a while so can't be certain this is still the case.
It looks like everything that I am expecting to go into my "Aggregators" channel is going into the "Referring Domains" channel (that I use for another site), even though I have excluded this site as per below:
Hi @alexjbaker11 The set up seems to be correct, no issues there. Please check with the 'Last touch channel report' to check for Channel name & as mentioned by @amgup also check 'Last touch channel detail' report if you see query param value in that report.
If you still don't see attribution to the correct channel as you'd expect, you check 2 things: 1. Verify if the url with query params is in correct format, for marketing channel processing rule to extra query param info.
2. If you really want to know the reason what went wrong, I suggest pulling raw data via data feeds and check for those hits, that would definitely give you the answer.